Randomized, controlled clinical trial of safety and plasma concentrations of diclofenac in healthy neonatal foals after repeated topical application of 1% diclofenac sodium cream

Objective To determine the plasma pharmacokinetics and safety of 1% diclofenac sodium cream applied topically to neonatal foals every 12 hours for 7 days. Animals Twelve 2- to 14-day old healthy Arabian and Arabian-pony cross neonatal foals. Procedures A 1.27-cm strip of cream containing 7.3 mg of diclofenac sodium (n = 6 foals) or an equivalent amount of placebo cream (6 foals) was applied topically to a 5-cm square of shaved skin over the anterolateral aspect of the left tarsometatarsal region every 12 hours for 7 days. Physical examination, CBC, serum biochemistry, urinalysis, gastric endoscopy, and ultrasonographic examination of the kidneys and right dorsal colon were performed before and after cream application. Venous blood samples were collected at predefined intervals following application of the diclofenac cream, and plasma diclofenac concentrations were determined by liquid chromatography–mass spectrometry. Results No foal developed any adverse effects attributed to diclofenac application, and no significant differences in values of evaluated variables were identified between treatment groups. Plasma diclofenac concentrations peaked rapidly following application of the diclofenac cream, reaching a maximum of < 1 ng/mL within 2 hours, and declined rapidly after application ceased. Conclusions and Clinical Relevance Topical application of the 1% diclofenac sodium cream to foals as described appeared safe, and low plasma concentrations of diclofenac suggested minimal systemic absorption. Practitioners may consider use of this medication to treat focal areas of pain and inflammation in neonatal foals.